Conventionally, ultrasonic diagnostic apparatuses have been used which operate with power supplied from a commercial AC power source. In recent years, however, ultrasonic diagnostic apparatuses which allow switching between a commercial AC power source and a rechargeable battery have been used in order to deal with various use modes of ultrasonic diagnostic apparatuses. PTL 1, for example, discloses a configuration in which a power source unit having a rechargeable battery is connected to an ultrasonic diagnostic apparatus, and this power source unit can switch between an AC power source and the battery. Specifically, in this configuration, when an input from the AC power source is detected, the power from the AC power source is supplied to the ultrasonic diagnostic apparatus, and when no input is detected from the AC power source, the power from the battery is supplied to the ultrasonic diagnostic apparatus.